Posts Tagged ‘irrigation’

State Conservationist Russell Morgan, USDA Natural Resources Conservation Service (NRCS), encourages Delaware irrigators to use the recently released Delaware Irrigation Management System (DIMS). DIMS is an online tool designed to provide members of the Delaware agricultural community access to irrigation scheduling software that is streamlined and tailored to Delaware.

This system, which utilizes input from the user, input from existing DEOS weather stations, and physical data from the environment, is designed for several irrigated crops in Delaware: corn, soybean, sweet corn, cucumbers, watermelons, cantaloupes, lima beans, and peas. Developed by staff at the University of Delaware’s Delaware Environmental Observing System (DEOS), the project was funded by grants from the USDA Natural Resources Conservation Service and the Delaware Department of Natural Resources and Environmental Control.

“Growers using DIMS will be able to manage their irrigation water more efficiently, which has a multiplying effect on an operation,” said Morgan. “Results include increased yields which lead to higher profits; there’s improved water quality resulting from efficient utilization of nutrients; and also water conservation, which reduces water waste and can lower operating costs.”

Irrigation scheduling software is nothing new; however, this software was written specifically for Delaware. Also, many software applications often require the manual entering of weather data. DIMS is the only current software for Delaware that is automatically updated with weather data.

DIMS uses an irrigation scheduling method based on a basic water balance. The amount of water lost from the soil surface (evaporation) plus the amount of water used by the crop (transpiration) is calculated and tracked and compared to inputs from rainfall, soil moisture measurements, and irrigation to determine the amount of water available in the soil to a particular crop. Through this method, which is generally referred to as the “checkbook” method, a user hopes to optimize the amount of soil water available to the crop, thus reducing crop stress, improving crop yield, and maximizing nutrient uptake by the crop.

DIMS is streamlined and tailored to Delaware and was created to reduce the amount of effort required of the user both before and during the growing season. DIMS provides a straightforward, online interface that allows users to quickly determine if a field has adequate soil moisture to satisfy the crop’s water requirements and make immediate irrigation decisions.

The USDA NRCS has financial assistance available for Irrigation Water Management.

For more information regarding DIMS contact Kevin Brinson, DEOS Systems Manager, at kbrinson@udel.edu or by phone at 302-831-6906. For more information on NRCS programs and services in Delaware, visit www.de.nrcs.usda.gov or contact your local USDA Service Center. In Sussex County, call 302-856-3990 x 3; in Kent County, call 302-741-2600 x 3; in New Castle County, call 302-832-3100 x 3.

Irrigation is a critical management tool for producing high yielding and high quality vegetable crops. Scheduling irrigation for different vegetables grown under center pivot, travelling gun, or solid set overhead systems involves knowledge of the soil water holding capacity, the effective rooting depth of the crop (how deep water can be drawn by the crop), how efficiently water is being delivered (water losses to evaporation before it reaches the crop and how much water is lost to runoff), how much water is being used by the crop (transpiration) and how much water is being lost from the soil and wetted surfaces directly (evaporation). The combination of transpiration and evaporation losses is termed evapotranspiration.

To schedule irrigation, the goal is to replace water lost through evapotranspiration without excessive runoff or excessive loss through percolation out of the root zone. Another factor to consider is the permissible water depletion; how much will you allow the soil to dry down between irrigations. For most crops we set this at 50% of the water holding capacity of the soil. However, for some shallow rooted crops you may want to keep that value lower (only allow for 40% depletion between irrigations). By knowing how much water is being lost and how much is left in the soil, you can determine when to irrigate and how much to irrigate.

In classic work done by the University of Delaware Agriculture Engineering Department in the 1970s and 1980s, water use estimates were developed for a number of vegetable crops. These values remain useful guides for irrigating these crops. A summary follows:

Sweet Corn: Water use 40 days after planting was 0.10 inches per day, water use 60 days after planting was 0.23 inches per day and water use at peak (75 days) was 0.26 inches per day.

Potatoes: Water use 40 days after planting was 0.15 inches per day, water use 60 days after planting was 0.27 inches per day and water use at peak (80 days) was 0.37 inches per day.

Peas: Water use 40 days after planting was 0.16 inches per day and water use 60 days after planting was 0.33 inches per day (peak).

Lima Beans: Water use 20 days after planting was 0.13 inches per day, water use 40 days after planting was 0.25 inches per day, water use 60 days after planting (peak) was 0.33 inches per day and water use 80 days after planting was 0.23 inches per day.

Cucumbers: Water use 20 days after planting was 0.13 inches per day, water use 40 days after planting was 0.27 inches per day, and water use at peak (50 days) was 0.30 inches per day.

Watermelons: Water use 20 days after planting was 0.10 inches per day, water use 40 days after planting was 0.23 inches per day, water use 60 days after planting (peak) was 0.30 inches per day, water use 80 days after planting was 0.28 inches per day and water use 100 days after planting was 0.22 inches per day.

Tomatoes: Water use 20 days after planting was 0.15 inches per day, water use 40 days after planting was 0.27 inches per day, water use 60 days after planting (peak) was 0.33 inches per day, water use 80 days after planting was 0.28 inches per day and water use 100 days after planting was 0.25 inches per day.

Many of our hay and pasture species are just beginning the rapid growth phase that occurs each spring. More and more hay and pasture fields are set up to receive irrigation. The limited rainfall the southern half of the state has received so far this spring means that the soil water supply will be rapidly depleted as the cool-season hay and pasture grasses enter the rapid growth phase. Orchardgrass, in particular, since it matures earlier than many of the other species we grow, will be using large quantities of water during the next few weeks. If you are set up to irrigate hay and pasture fields, now is the time to begin the irrigation system. Try not to let the soil moisture levels be lowered to the point that water stress symptoms actually show up on the crop. As the species enter the rapid growth phase of spring, water use will increase from about a tenth of an inch of water per day to a quarter inch or more water per day. To keep fields actively growing, be sure to replace that quantity of water each week. When warmer temperatures occur in June, water use can increase to that approaching corn (about a third of an inch per day) so your irrigation regime will need to increase as summer approaches. Keep in mind that you will need to stop irrigation long enough for the soil to dry enough to support haying and baling equipment without causing significant compaction. It’s also usually best to wait until the crop begins regrowth before resuming irrigation so that you do not encourage weeds.

It also is time to get nitrogen (N) out on irrigated and non-irrigated hay and pasture fields. For hay, the latest research from Pennsylvania State University and Dr. Marvin Hall’s team shows that you should be applying about 50 lbs of N per acre per ton of expected yield. This is a good compromise between maximum economic yield from the hay and the risk of high nitrate levels in the hay if the crop becomes very drought stressed. For pastures, our N recommendations still vary based on the amount of legume in the pasture. If pastures contain a one to one ratio of legume to grass (50 percent of the biomass-forage-comes from the legume), additional N fertilizer will not be needed. If the legume component makes up between 25 and 50 percent of the forage, then apply about 25 lbs N/acre and if there is less than 25 percent legume in the forage, you may need as much as 50 lbs N/acre to maximize productivity of the pasture.

With the higher prices available for corn, it would seem that profitable corn production is assured. However even if a profitable season is highly likely where either irrigation or timely rainfall is plentiful, there are many agronomic practices that can be used to improve the chances of success. The first one that comes to mind relates to the yield curve as affected by planting date. In research conducted in Delaware and surrounding states in the past, we’ve seen slightly (3 to 5 percent) lower yields when corn is planted before the first of May. Large acreage growers often feel the need to begin planting early just to be able to finish planting their corn acreage before yields begin to decline due to late planting. Small acreage growers can get restless seeing others out planting corn and move to plant before the ideal window, the last week of April and the first week of May. Growers can still satisfy the need to plant enough acres to finish in time or the urge to get into the field early by dividing their fields up into high yield potential fields, moderate yield potential fields, and low yield potential fields. Plant the low yield potential fields at the earliest opportunity and again at the end of the corn planting window if all of the acres aren’t completed early or if special soil conditions preclude entering the field until later in the spring. If all the low yield potential fields are planted and more time is available before the ideal planting window, growers should move to the medium yield potential fields. As soon as the ideal window opens, growers should change to the best high yield potential fields. The higher yield potential during this period can add quite a bit of extra corn to your final farm yield. Once past the first week of May or once all the best fields are planted, move on to finish with the medium yield potential fields and finally those low yield potential fields with special problems are that weren’t planted earlier.

On no-till fields, be sure to use row sweeps or row cleaners to help warm up the soil at the planted rows. Soil temperatures high enough for rapid uniform germination are essential in obtaining the highest possible yield potential. Also, consider using hybrids ranked highest for cold tolerance since improvements have been made on that front in the past few years.

The same thing applies to deciding where to apply the most fertilizer dollars. You should always aim at fertilizing your high yield potential fields with enough fertilizer to obtain maximum economic yields (MEY). Recognizing that yield from your medium yield potential fields will be lower than that in the high potential fields, you should reduce your input levels on these fields. For the low yield potential fields, keep the number of fertilizer dollars spent on these fields to the minimum needed to obtain the average yield you expect off these fields. By adjusting your fertilizer rates for each field, you can reduce your overall fertilizer bill as well as ensure that your get the biggest bang for your buck from your best fields.

I think it is safe to say that seed costs are higher than ever nowadays. Again, choose the best hybrids and use the highest (best) seeding rate on your best fields. Not only will you get more for your money but since you’ll be planting this expensive seed at the ideal time, your plant stands will be better and less seed will be wasted. In other words, use your race horse hybrids on your better fields. For the medium and low yield potential fields, choose the work horse hybrids which can tolerate the less favorable growing conditions and still respond if the growing season turns out to be a good one. Adjust your seeding rate slightly up when planting early to help ensure better stands and lower your seeding rate later in the planting window when the soil is warmer and germination conditions are closer to ideal. In addition, you won’t waste as much seed in fields that have lower potential.

A final suggestion on irrigated land would be to consider irrigating early if the dry conditions persist. A recent visit down the state showed very low water levels and therefore water tables in much of central and southern Delaware. Although corn uses very little water when it is early in its growth cycle, it is highly likely that the subsoil layers are not at field capacity. It is highly advisable to bring soil moisture levels in both the top soil and subsoil close to their maximum water holding capacity early in the season so that the corn will not suffer early water stress. This also will give you a base or buffer so that later in the season during tassel, silking, and seed fill, the irrigation system can keep up better with the crop’s water demand.

The UD irrigation program in Georgetown, with cooperation and support from NRCS, has evaluated the performance of over 170 center pivot irrigation systems on Delmarva. There are some problems we have observed that growers can easily correct. As we enter a new growing season, here are some suggestions:

1. Check the pressure gauge and replace if broken or missing. This is simple and cheap, but improper pressure can significantly alter the performance, particularly on systems that do not use pressure regulators.

2. Take time to ride or walk the length of the system while it is operating and replace any missing sprinklers, spray plates, plugs etc. and unplug any plugged tips. Sprinkler flow rate increases down the length of the system, and so each sprinkler is sized according to the distance from the pivot. A single plugged tip at 700 ft that causes reduced or no irrigation over a 10 ft section affects an area of 1 acre over a complete circle. The same situation at 1100 ft affects almost 1.6 acres. If replacing a sprinkler or tip, be sure to use the correct size, as we have observed that incorrectly sized sprinklers are a common source of unwanted variability.

3. It is difficult to accurately determine how uniformly a pivot system is applying water, or how much it is applying at any given timer setting. The best test involves setting out cans or rain gauges every few feet along the length of the system, as we do in the evaluation program. This gives a very accurate average and also catches any points with too little or too much water. This is not feasible for most growers, but perhaps checking the volume of water in 5-10 cans or gauges spaced along the system would identify major problems and give an indication of the average irrigation amount at the particular timer setting. Manufacturers provide a chart that shows the irrigation amount at various timer settings. We have observed that charts are generally quite accurate on new and unaltered systems, and are built in on systems with programmable electronic panels. However, on older systems, especially if you have replaced some components or are running at different pressures, taking the time to find out if the system is putting out what you think it is can be a valuable exercise, particularly considering the rising cost of pumping water.

Wheat irrigation is a subject of considerable discussion. Does it pay? When should wheat be irrigated? How much should wheat be irrigated? When should you stop irrigating wheat? The following are some thoughts on the subject.

Irrigation does not always show an increase in yield. In fact, irrigation at the wrong time could potentially reduce yields. On average, a 3-7 bushel increase in yield has been seen with irrigation looking at yield maps. At today’s prices, a 7 bushel increase would be over $60 more per acre. This must be weighed against the cost of irrigation. Fuel costs alone to apply 1.5 inches of water would be $19 per acre.

Wheat water use is minimal until jointing, when the plant has some height to it. At jointing, wheat will use between 0.2 and 0.25 inches of water per day. At boot and heading stages, wheat is using around a quarter of an inch a day, and during grain development through the milk stage, wheat will use about 3 tenths of an inch a day. Once wheat hits the dough stage, water use drops off considerably.